fenjithe Quality of the Averrhoa Qiramboia. ^59 
the leaves is different from that of other pinnated plants. In 
the laft a great uniformity fubfifts in the refpedtive pofition of 
the leaves on the pinna ; but here feme will be feen on the 
horizontal plane, fome raifed above it, and others fallen under 
It; ' and in an hour or fo, without any order or regularity, which 
I could obferve, all thefe will have changed their refpe&bve 
pofitiorts. I have feen a leaf, which was high up, fall down ; 
this it did as quickly as if a ftrong impreffion had been made 
on it, but there was no caufe to be perceived. 
Cutting the bark of the branch down to the wood, and even 
feparating it about the fpace of half an inch all round, fo as .to 
flop all communication by the. veftels of the bark, does not for 
the ftrft day affedt the leaves, either in their pofition or their 
aptitude for motion. 
In a branch, which I cut through in fuch a manner as to 
leave it fufpended only by a little of the bark no thicker than a 
thread, the leaves next day did not rife fo high as the others ; 
but they were green and frefti, and, on being touched,, moved, 
but in a much lefs degree than formerly. 
After fun- fet the leaves go to bleep, £rft moving down fo as • 
to touch one another by their under fides ; they therefore per- 
form rather more extenfive motion at night of lhe.mfelves.dian 
they can be made to do in the day-time by external imprefhons. 
With a convex lens I have colleded the rays of the fun on a 
leaf, fo as to burn a hole in it, without occafioning any motion* 
But when the experiment is tried on the petiolus, the motion is 
as quick as if from ftrong percuffion, although the rays were 
not fo much concentrated as to caufe pain when applied in the 
fame degree on the back of the hand ; nor had the texture of 
the petiolus been any ways changed by this .; for next day it 
\-OL« LXXVo ,B b b could 
